the correct answer here is D
D. Nobles stopped supporting the emperor.
The period of the warring states happened during the Zhou dynasty. it occured after the barbarians attacked the capital and ransacked it resulting to financial weakness. The zhou king could no longer support a large army and lost the support and control of the fiefdoms or states who started fighting against each other.
I believe that they are just cousins, I don't remember much. Sorry if i got it wrong